Skin clamp



Nov. s, 1946. M WLOR 2,410,664

SKIN CLAMP Filed Jan. 20, 1944 INVENTOR MA/PT/A/ ILA WLOI? BY hf /Z@ A TTO/PNE Y Patented Nov. 5, 1946 glitter 2,410,664 skin CLAMP Martin T. Lawlor, Waterbury, Conn, assignor, by mesne assignments, to Irving Rossi Application January 20, 1944, Serial No. 518,928

Serial No. 441,153, filed April 30, 1942, entitled- Fasterner, now Patent No. 2,354,480, there is described a clamp of this character comprising substantially a housing or body having a work engaging base provided with an opening f a di ameter substantially equal to the perforations in the aligned plates or other work to be assembled. A retainer comprising a pair of resilient legs having shoulders at their outer ends and operable towards each other is arranged to slide through said opening, a spreader arranged in fixed relation to said body being interposed to space said legs apart. The retainer is urged inwardly of said body into retracted or clamping position by means of a coil spring interposed between its inner end and said body, whereby to cause said shoulders to engage the outer surface of said base in the non-operative position of the device or to resiliently clamp the perforated sheets or other work between said shoulders and said base in the operative or use position of the device.

The clamp is applied to and removed from the work by compressing the spring by the aid of a suitable tool such as a plier appliedto the housing and the inner end of the retainer, whereby to cause the legs to project outwardly of the body beyond said spreader in such a manner as to approach each other or flex sufiiciently to enable their insertion through and removal from the perforations.

Clamps of this type are required in considerable numbers,in particular in the manufacture of airplanes, to assist in the riveting of the metal sheets or, skins to the structure of the planes, in locating lock or stop nuts in proper position for securing them to a cowling or other metal structure and other applications.

Practice has shown that in order to ins re safe riveting of the sheets, considerable clamping forces are required to prevent misalignment of the sheets or plates during the riveting operation and other drawbacks. This makes it necessary to employ heavy clamping springs which in turn require a substantial force to be exerted by the pliers or other tools during the insertion .and removal operations, resulting in considerable 15 Claims.

2 stresses to which the clamps have to be subjected in use.

' As a result thereof, it has been experienced that the clamps may fiy apart when parts thereof become accidentally damaged during use, in particular when the heads or shoulders of the retainer are accidentally sheared or broken off. This may result in serious accidents and danger to the workmen in the neighborhood, as is understood.

An object of the present invention is therefore, to'improve the safety factor of clamps of this type by preventing the parts to be ejected forcibly if one of the elements becomes accidentally damaged or broken.

A further object is to provide a clamp of this type, which'is both simple in construction and efficient in operation and, Which can be easily and safely installed and removed from the work without complicated tools or special operations.

Further objects and aspects of the invention will become more apparent from the followin detailed description taken in reference to the accompanying drawing forming part of this specification, and wherein:

Figure 1 is an elevation, partly broken away, of a clamp embodying the principles of the invention; Figure 2 is a side view shown partly in cross section, of the clamp according to Figure 1; Figure 3 is a cross-section taken on line 33 of Figure 2; and Figure 4 is a cross-section taken on line 44 of Figure l.

Like reference characters identify like parts in the different views of the drawing. The clamp shown comprises a cup or thimbleshaped body or housing Ill having a flange H at its open end and a sheet engaging bottom or base l2 providedwith a central bore or opening it. The latter has a diameter substantially equal to the diameter of the perforationsin the work to be assembled such as two superposed perforated plates A and B shown for illustration in the draw- A plunger or. retainer comprising, in the example shown, a member of U- or hairpin shape having a pair of resilient legs It provided with projections or shoulders [5 at their outer ends, is arranged to slide through the opening H3 in the body 1 it with said legs being held in spaced apart osition bythe, depending portion it of a substantially T-shaped spreader interposed between said legs and having a cross-arm ll resting against the inside of the bottom or sheet engagingbase1l2. A cap or inverted cup-shaped washer lileisplaced over the spreader cross-arm H to provide a recess for the latter, said washer having a central opening for passing the legs M and being provided with diametrical recesses in its cylindrical portion as indicated at I1 and adapted to receive the ends of the cross-arm ll, whereby to lock the spreader against or prevent relative movement with respect to said washer. Alternatively, the spreader cross-arm I! may be mounted loosely within the recess provided by the spreader l8.

In the example illustrated, the legs 14 which one hand and the flange H on the other hand. During compression, the legs will slide beyond the spreader 16, whereby to cause sections I40 and shoulders 15 to approach each other or to flex sufliciently to enable their insertion through and removal from the perforations in the plates A and B or other work to be assembled.

The housing and remaining elements may be hardened to withstand the stress and forces exerted thereon and to reduce the size of the clamp to a minimum. Sleeve 2! may consist of brass are preferably constructed from a single length of wire of half round or segmental cross-section, have inner parallel portions Ma followed by intermediate portions Mb and outer portions 140 which may be bent inwardly as shown in the applications mentioned above so as to approach each other by their own spring tension when the legs are projected beyond the spreader it by compression of the spring during the insertion and removal operations. Alternatively, the lower portions I40 may be substantially parallel or normally spaced similar to the portions Mb and adapted to flex sufficiently to allow insertion through and removal from the sheet perforations.

The purpose of the washer i8 is to locate the spreader to prevent canting thereof and to serve as a base for a coiled clamping spring 26 encircling the legs l and having its lower end engaging saidwash-er and having its upper end engaging the inner end of the retainer. In this manner, the washer [8 acts both as a balancing means for the fastener, while at the same time taking the thrust of the spring away from the spreader arm I! as well as fromthe housing 10, resulting in a favorable distribution of the forces exerted by the spring without producing excessive stress on the parts and preventing the legs and spring from bending sideways or canting in the manner pointed out. This in turn enables the size of the parts and the clamp to be held at a minimum.

The washer 58 may be omitted if a weaker spring is used, suiiicient in some cases, in which case the lower end of the spring engages the spreader cross-arm I? and in this manner prevents the spreader from moving in the longitudinal direction by maintaining it in bearing engagement with the inside of the bottom or base In order to further improve the symmetry or balance of the clamp, there is provided a cylindrical sleeve 2! interposed between the legs 14 and the spring 20, said sleeve having an upper flange or shoulder 22 engaged by the upper end of the spring and terminating in an outwardly flaring skirt or rim '23 secured to or engaging the head or cap 24 secured to the inner end of the legs M. Cap 24 for this purpose has an inwardly flaring skirt 24' engaging the skirt 23 of the sleeve 2!. The cap in the example shown is secured to the legs [4 by means of a pin passed through a lateral opening in the cap, said pin fitting snugly within the upper bent portion of the legs [4 and being secured or held in place by staking or deforming the cap or in any other suitable manner. The sleeve 21 advantageously has a close fit within the coil spring and the legs M to obtain an optimum straightening or balance of the entire retainer unit comprising the parts l4, 2 I, 24 and 25 within the spring 20.

In use, spring '20 is compressed by applying a suitable tool such as a plier having jaws or'sockets engaging the outer surface of cap 23 on the and may have a length designed to act as a stop to limit the compression of the spring when the lower end of the sleeve engages the washer Hi.

In a clamp of this type intended for many thousands of insertion and removal operations, it may happen that due to wear and other causes, the parts, in particular the projections or shoulders 15, may be damaged or broken away, in which case the spring and/or retainer will be ejected forcibly or fly apart haphazardly, whereto involve serious danger and operator hazard.

According to the present invention, this drawback is avoided and adequate operating safety insured by locking or anchoring the spring 20 to the body or housing It! on the one hand and to the retainer on the other hand, in such a manner, that, with the spring becoming suddenly relaXed from the compressed to its expanded position due to damage or breakage of one of the parts, in particular the shoulders or projections [5, both the spring or any of the other remaining parts will be prevented from being ejected forcibly or flying apart and endangering workmen in the neighborhood.

For this purpose, at an intermediate part of the housing ii], a plurality of preferably equally spaced nibs or inward projections 26 are struck in position, so that they will at least inter-engage one or more turns at the inner end of the spring 20 adjacent to the spreader l1 and washer l8. Furthermoreyat the opposite end of the device the sleeve 2| has its side walls diametrically skived or punched as shown in 21 leaving two connecting'straps or projections 28. The latter, after the spring has been assembled against the flange 22 of the sleeve 2 i, are collapsed or folded outwardly back upon themselves to provide nibs or outward projections inter-engaging between .two turns at the opposite end of the spring 20 and holding the same permanently connected to the sleeve 21 and in turn to the legs 14.

By this construction, accidental breakage of the shoulders l5 and sudden slipping of the legs M through the openings in the plates A and B and the housing is due to expansion of the spring 20, will result in a prevention of the parts being forcibly ejected and flying apart haphazardly by the spring It being locked to the housing I8 by the nibs or projections 26 and by the retainer being locked to the spring via the cap 25: and sleeve 2! by the nibs or projections 28 in the manner described and understood from the foregoing.

It will be understood that the locking of the spring 29 to the body l0 and to the sleeve ill or retainer may be effected in various other manners which will readily suggest themselves to those skilled in the art, the particular method shown and described for illustration having the advantage of enabling the use of simple stamping and punching operations.

The sleeve 21' may be secured to the cap 24 in any other suitable manner, the method shown in the drawing having the advantage of involving d a minimum of parts and connecting operations.

Furthermore, the looking o anchoring of the spring to the housin and retainer, respectively, is not limited to the specific type of clamp shown in the drawing but may be used with equal advantage 'in any other clamp construction comprising essentially a body, a retainer slidable with respect to said body and having at least one shoulder or other clamping member at its outer end and a spring interposed between the inner end of said retainer and said body to retract said retainer and to urge said shoulder into clamping engagement with said body. In a clamp of this type, breakage of the shoulder or other-clamping member would result in a sudden expansion of the spring and forcible ejection of the parts in the absence of the precautionary features proposed by the invention to hold the parts together by locking the spring to both the housing and retainer in the manner shown and described. Thus, the spreader or other complementary hole-filling element cooperating with the retainer may be constructed and mounted as shown in any of the prior art constructions and the spring may directly engage the inside of the bottom or base in accordance with the broad scope of the invention.

Accordingly, it will be evident that the inventionisnot limited to the specific details and constructions shown and disclosed herein for illustration, but that the underlying principle and novel thought are susceptible of numerous variations and modifications coming Within the broader scope and spirit of the invention as defined in the appended claims. The specification and drawing are accordingly to be regarded in an illustrative rather than in a limiting sense.

I claim:

-1. In a clamp device, a body having a base provided with an opening, a retainer slidable through said opening and having at least one shoulder at its outer end, a coil spring encircling said retainer and interposed between the inner end of said retainer and said body to normally retract said retainer and to cause said shoulder to engage said base, said-body and retainer being provided with projections inter-engaging adjacent turns at the opposite ends of said spring, whereby to lock said spring to both said body and said retainer.

-2. In a clamp device, a cylindrical body having a base provided with an opening, a retainer slidable through said opening and having a pair of resilient legs provided with shoulders at the outer ends thereof, a spreader in fixed relation to said body and interposed between said legs, a coil spring interposed between the inner end of said retainer and said body to normally retract said retainer and to cause said shoulders to engage said base, said body and retainer being provided with projections inter-engaging adjacent turns at the opposite ends of said spring, whereby to lock said spring to both said body and saidretainer.

3. In a clamp device, a cup-shaped body having a base provided with a central bore, a retainer slidable through said bore and having at least one lateral projection at the outer end thereof, a coil spring interposed between the inner end of said retainer and said body to normally retract said retainer and to cause said projection to engage said base, said body being provided with instruck internal projections inter-engaging adjacent turns at one end of said spring and said retainer having means provided with outward projection-s inter-engagingadjacent turns at the opposite end of said spring, whereby to lock said spring both to said body and said retainer.

4. In a clamp device, a cup-shaped housing having a base provided with a central bore, a retainer slidable through said bore and havin a pair of resilient legs operable towards each other and provided with shoulders at the outer ends thereof, a spreader in fixed relation to said body and interposed between said legs, a coil spring encircling said retainer and interposed between said body and the inner end of said retainer to normally retract said retainer and to cause said shoulders to engage said base, said body being provided with in-struck internal projections inter-engaging adjacent turns at one end of said spring and said retaine including means provided with projections engaging adjacent turns at the opposite end of said spring, whereby to lock said spring to both said body and said retainer.

5. In a clamp device, a cup-shaped body having a base provided with a central bore, a retainer slidable through said bore and having at least one lateral projection at the outer end thereof, a coil spring encircling said retainer and interposedbetween said base and the inner end of said retainer to normally retract said retainer and to cause said projection to engage said base, a sleeve in fixed relation to the inner end of said retainer and interposed between said spring and said retainer, said body being provided with at least one inward projection inter-engaging adjacent turns atone end of said spring and said sleeve having atleast one outward projection inter-engaging adjacent turns at the opposite end of said spring, whereby to lock said spring to both said body and said retainer.

6. In a clamp device, a cup-shaped body having a base provided with a central bore, a retainer slidable through said bore and having a pair of resilient legs provided with shoulders atthe outer ends thereof, a spreader in fixed relation to said body and interposed between said legs, a coil spring encircling said retainer-and interposed between said base and the inner end or" said retainer to normally retract said retainer and to cause said shoulders to engage the outsideof said base, a sleeve in fixed relation to the inner end of said retainer and interposed between said spring and said retainer, said body being provided with at least one in-struck internal projection inter-engaging adjacent turns at one end of said spring and said sleeve bein provided with at least one outward projection inter-engaging adjacent turns at the opposite end of said. spring, whereby to lock said spring to both said body and said retainer.

7. In a clamp device, a cup-shaped housing having a base provided with a central bore, a retainer slidable through said bore and having resilient legs operable towards each other and provided with shoulders at theouter ends thereof, a spreade resting against the inside or" said base and having a portion interposed between said legs, a coil spring encircling said lretainer having one end engaging, the inner endof said retainer and arranged to maintain said spreader in bearing arrangement with said base, said spring drawingsaid retainer inwardly of said. body to internal projection inter-engaging adj acentpturns at one-end of said spring and saidsleeve being provided with at least one optward projection engaging adjacent turns at the opposite and of said spring, whereby to lock said spring to both said body and said retainer.

8. In a clamp device, a cup-shaped housing having a base provided with a central bore, a retainer slidable through said bore and having at least one lateral projection at the outer end thereof, a cap secured to the inner end of said retainer, a sleeve in fixed relation to and having a flange adjacent to said cap, a coil spring encircling said retainer having one end engaging said flange and having its other end engaging said body to retract said retainer and to cause said projection to engage the outside of said base, said body being provided with at least one inward projection inter-engagin adjacent turns at one end of said spring and said sleeve being provided with at least one outward projection inter-engaging adjacent turns at the'opposite end of said spring whereby to lock said spring to both said body and said retainer.

9. In a clamp device, a cup-shaped housing having a base provided with a central bore, a retainer slidable through said bore and having at least one lateral projection at the outer end thereof, a, cap having an inwardly flaring rim and secured to the inner end of said retainer, a sleeve having a flange at one end terminating in an outwardly flaring rim engaging the rim of said cap, a coil spring encircling said retainer and interposed between said flange and said body to retract said retainer and to cause said projection to engage the'outside of said base, said body being provided with at least one inward projection inter-engaging adjacent turns at one end of said spring and said sleeve being provided with at least one outward projection inter-engaging adjacent helices at the opposite end of said spring, whereby to lock said spring to both said body and said retainer.

10. In a clamp device, a cup-shaped housing having a base provided with a central bore, a retainer slidable through said bore and having at least one lateral projection at the outer end thereof, a cap secured to the inner end of said retainer, a sleeve in positive connection with said cap and having a flange adjacent to said cap, a coil spring encircling said retainer and interposed between said flange and said body to retract said retainer and to cause said projection to engage the outside of said base, said body being provided with at least one in-struck projection interengaging adjacent turns at one end of said spring and said sleeve having adjacent apertures and at least one connecting strap therebetween folded back upon itself to provide an outward projection inter-engaging adjacent turns at the opposite end of said spring, whereby to lock said spring to both said body and said retainer.

11. In a clamp device, a cup-shaped housing having a base provided with a central bore, a retainer slidable through said bore having a pair of resilient legs provided with shoulders at the outer ends thereof, a spreader resting against the inside of said base and having a portion interposed between said legs, a cap secured to the inner end of said retainer, a sleeve in positive connection with said cap and having a flange adjacent to said cap, a coil spring encircling said retainer having one end engaging said flange and arranged to maintain said spreader in bearing engagement with said base, said sleeve bein interposed between said retainer and said spring, said body being provided with a plurality of equally spaced in-struck internal projections inter-engaging adjacent turns at one end of said spring and said sleeve being provided with adjacent apertures and intervening connecting straps folded back upon themselves to provide outward projections inter-engaging adjacent turns at the opposite end of said spring, whereby to lock said spring to both said body and said retainer.

12. In a clamp device, a cup-shaped housing having a base provided with a central bore, a retainer slidable through said bore and having a pair of resilient legs provided with shoulders at the outer ends thereof, a spreader resting against the inside of said base and having a portion interposed between said legs, a cap having an inwardly flaring rim and secured to the inner end of said retainer, a sleeve having a flange at one end terminating in an outwardly flaring rim engaging the rim of said cap, a coil spring encircling said retainer and interposed between said flange and housing and arranged to maintain said spreader in bearing engagement with said base, said spring drawing said retainer inwardly of said body to urge said shoulders spaced by said spreader into clamping engagement with the outside of said base.

-13. A device for temporarily clamping together perforated sheets in superposed relation comprising a body having a sheet engaging base provided with an opening, a sleeve movable relative to said body, a retainer locked in said sleeve for movement therewith, said retainer carrying means on one end projecting through said opening adapted for engagement against the underside or" the sheets being clamped, a spreader for said retainer resting on the inner face of said base, and a spring having one end resting on said spreader and its other end locked to said sleeve for drawing said sleeve and retainer inwardly of said body to urge said one end of the retainer into sheet clamping engagement.

14. A device for temporarily clampin together perforated sheets in superposed relation comprising a body having a sheet engaging base provided with an opening, a hollow sleeve movable relative to said body and having a head on one end thereof, a retainer locked in said sleeve for movement therewith, said retainer including a pair of legs projecting through said opening and formed with means adapted for engagement against the underside of the sheets being clamped, a spreader for said legs, a spring interposed between the head of said sleeve and said spreader for drawing said sleeve and retainer inwardly of said body to urge the means on said legs spaced by said spreader into sheet clamping engagement, and means on said sleeve and body for locking said spring to limit its movement in one direction.

15. A device for temporarily clamping together perforated sheets in superposed relation comprising a body having a sheet engaging base provided with an opening, a sleeve movable relative to said body, a retainer locked in said sleeve for movement therewith, said retainer including means adapted for engagement against the underside of the sheets being clamped, a spring surroundin said sleeve and functioning to press said sleeve and retainer inwardly of said body to urge the means on said retainer into sheet clamping engagement, and means on said sleeve and body for locking said spring to limit its movement in one direction. 7

MARTIN T. LAWLOR. 

